Prerequisites for Andrew Ng's Machine Learning Course
This course is focused on machine learning using MATLAB, which is not practical nowadays as it is a programming language used specifically for computing, and cannot display GUI or communicate through the network. The language is powerful but limited in some ways. Nowadays most people use python for machine learning, as it is versatile and can connect to other backend like C++, java, JavaScript easily. The language is also a general language, and unlike MATLAB can do many things not limited to computing.

If you really want to join this course, I would recommend first learning MATLAB language and also learn basic calculus like derivatives. This would greatly help on your learning of the course.

However if you want to here serious about machine learning, I would encourage you to enroll in the Deep Learning specialization also by Andrew Ng on Coursera.
https://www.coursera.org/specializations/deep-learning
This course uses python as the programming language and teaches more modern approaches to deep learning like recurrent neural networks, convolutional neural networks and more. It also talks more about application of neural network. There is also theory, but it also talks about application of a specific algorithm and how it works. 

Hope I can help you.